The invention refers to a method of producing sewing machine needles in general.
Particularly the invention refers to a method of producing sewing machine needles from a cylindrical length of wire.
The present invention uses die pressing, namely compression molding in which, starting from a diameter of the length of wire corresponding to the thickness of the needle butts, the length of wire is reduced approximately to the final cross-sectional size over at least the length of the needle shank and of a section and, furthermore, in the region of the needle shank, thread grooves are pressed in from the curved outer surfaces of the length of wire, the reduction in cross section being effected by pressing opposite portions of wire material so as to form laterally projecting flat fins which leave between them the transversely convexly curved outer surfaces which are in the final diameter, the flat fins being removed in a subsequent step, and with two coaxially oriented needle blnaks being worked simultaneously.
This compression molding from the solid blank represents a clear advance in manufacture as compared with the convectional, frequently time-consuming method of reduction by rotary press, since almost the complete final contour of the needle is obtained in a manner which is gentle to the structure and in a single working stroke.
The object of the present invention is to use and to further enhance this basic method of the invention such that on the one hand there is a stable double-needle blank, and on the other hand, however, the critical point region will be held as free of stress as possible. In particular, the pointing can be carried out more favorably.